Comment 9 for bug 1250875

I've just seen this on Ubuntu 16.04 on an EeePC and in one start up configuration it always happens and autologin always fails.

It seems to be highly dependent on what else is happening as lightdm is starting. When the problem occurs looking at the lightdm log shows that it is trying to log using a normal PAM lightdm session rather than an autologin PAM session. This leads to failure because the account being authenticated has a password and no password is being passed to PAM and the user is intentionally absent from the nopasswdlogin group.

Attaching /etc/lightdm/lilghtdm.conf, /var/log/lightdm/lightdm.log and PAM's /var/log/auth.log .